Here #2489 (address verification yields 451)
I found that Server should accept mail with an Envelope-Sender of <> (the null address), used
for processing bounce messages and an Envelope-Recipient of the sender of
the message.

Does it accept?

What do I do with message 451 ? And why the message is DEFERRED?
What means "not yet authorized" ?

You haven't given any information about whether this has happened before with this server or it's the first time it's happened nor even if you've ever sent them any mail before.

Originally Posted by shal

Is there a problem? What do I do with that?

The same answer would apply to both of your posts above, contact the mail administrator of those servers and ask them why they're rejecting your mail and/or see if you're on any sort of blacklist or RBL.

You haven't given any information about whether this has happened before with this server or it's the first time it's happened nor even if you've ever sent them any mail before.

The same answer would apply to both of your posts above, contact the mail administrator of those servers and ask them why they're rejecting your mail and/or see if you're on any sort of blacklist or RBL.

I tried to contact them but no answer so far.

Messages were deferred. They are dellivered but with some delay.

Our server is working 5 days since 21-05-2012. The IP that we were given from our ISP
was in
1. blacklist 88.blacklist.zap,
2. dynamic IP database MAPS - Stopping Spam at its Source DUL list
Both blacklists delisted IP 2 days ago.
IP is static. A,PTR,MX are OK. Open-relay test is OK. Users in our office can use mail via web interface only. 25 port for users is blocked by Zyxel Zywall USG50. The server is Ubuntu 10.04.4 LTS, Intel i3, 8Gb, RAID1. ~120000 emails ~80Gb of used space.

The first two days we got some mail rejected/deferred because of lists above.